Corynebacteria

Filename: Coryne.ppt

Outline

• Microbes
  • Corynebacterium,Listeria, Erysipelothrix

• Diseases
  • Diphtheria,Listeriosis, Erysipeloid

Corynebacterium: Habitat

• Skin

• upper respiratory tract

• GI tract

• Urogenital tract of humans

Cornyebacterium: Pathogens

• C. diphtheriae Diphtheria

• C.pseudotuberculosis humans sheep, cattle, suppurative lymphadenitis

• C. ulcerans humans pharyngitis

cattle -mastitis

• C. haemolyticum pharyngitis cutaneous infection

• C. pyogenes cattle, sheep, swine suppurative infection

• C.pseudodiphtheriticum endocarditis

C. xerosis

opportunistic infections

Group J K immunocompromised host

Related Organisms

Listeria monocytogenes

• Listeriosis

• Erysipelothrix rhusiopathiae
  • Erysipeloid

Diphtheria

DiphtheriaLaboratory diagnosis

• Speedy diagnosis

• Differentiate from commensals
  • “diphteroids”
  • nose & throat
  • C. xerosis C. hofmanni

• Throat swabs (confirmatory)
  • Blood Tellurite

• Virulence test

Corynebacterium

• Aerobic gram + rods

• -pleomorphic: club-shaped

• -pallisades

• -snapping cell division

• -metachromatic granules
  • methylene blue stain
  • volutin: polyphosphate

Cellular Morphology

• Gram positive rods

• “Snapping division”

• Palisade cells

• “Chinese letters”

Erysipelothrix

Specialized media

Tellurite:

black colonies

Not diagnosticallly significant

tellurite inhibits many organisms but not C. diphtheriae

Loeffler

best colonial morphology

Dextrose horse serum (1887)

now Dextrose beef serum

Blood tellurite

• Selective & differential medium

• Corynebacteria are resistant to tellurite
  • Reduced to tellurium

• Forms deposit in colonies
  • Colonies appear dark

• Biotypes
  • gravis, intermedius, mitis

Corynebacterium Biotypes

• C diphtheriae gravis

• C diphtheriae intermedius

• C diphtheriae mitis

• Helpful for epidemiological tracing

• Culture identified by biochemical tests.

Diphtheria

• Nasopharyngeal diphtheria
  • Pharyngeal
  • Larygngeal

• Cutaneous diphtheria

• Systemic complications

DIAGNOSIS MUST BE CLINICAL!!!!

Pharyngeal diptheria

• Inflammation
  • similar to strept throat

• Leucocytes
  • infiltrated
  • killed
  • embedded in fibrin clot

• TOXIN !!

Diphtheria Symptoms

• Pharyngitis

• Hypoxia
  • Choking
  • “Garitillo”

• Fever (103 F)

• Lymphadenitis

All SIGNS & SYMPTOMS CAUSED BY TOXIN

Diphtheria Pseudomembrane

• No True membrane

• Very few live cells

• Deposit of dead cells and protein

Pseudomembrane

• COVERS
  • tonsils,
  • uvula,
  • palate
  • nasopharynx
  • larynx.

• CONTAINS
  • bacteria
  • lymphocytes
  • plasma cells
  • fibrin
  • dead cells

DiphtheriaSystemic complications

• Nerves
  • toxic peripheral neuropathy
  • paralysis of short nerves
  • mouth, eye, facial extremities

• Cardiac
  • Congestive heart failure
  • high amount of toxin 48-72 hours
  • Low amount of toxin 2-6 weeks

Virulence Factors

• Diphtheria toxin !!!
  • blocks protein synthesis

• Dermonecrotic toxin
  • sphingomyelinase
  • increases vascular permeability

• Hemolysin

• Cord factor -Toxic trehalose
  • corynemycolic acid, corynemyolenic acid
  • 6,6’-di-O-mycoloyl- a,a’-D-trehalose

DiphtheriaToxin

• Blocks protein synthesis

• Protein 63Kd

• controlled by Tox gene

• lysogenic phage Beta-corynephage

• expressed if [iron] low

• 2 components A-B

Regulation of Diphtheria Toxin High [Fe 2+]

dtxR

Fe 2+ + apo DtxR

[Fe 2+ *DtxR]

p

C diphtheriae

dtxR= repressor protein

NO Toxin Produced

tox

Corynebacteriophage beta

o

P

Regulation of Diphtheria Toxin Low [Fe 2+]

Fe 2+ + apo DtxR

[Fe 2+ *DtxR]

Toxin Produced!!!

Toxin

• Part A
  • Active site
  • N terminal
  • Enzyme

• Part B
  • Binding site
  • Binds to membrane receptor
  • Transmembrane

Diphtheria toxin: Part A

• Active site

• Enzyme

• Blocks protein synthesis
  • ADP-ribosyl transferase
  • elongation factor 2 (EF2)

• Specific for mammalian cells
  • Prokaryotes have different EF2

Diphtheria Toxin: Part B

• Binding Site

• Binds to cell receptor

• Bound receptor internalized

• Endosome
  • Hydrolysed by protease
  • Disulfide broken
  • Part A released

Activation of Diphtheria Toxin

PPT Slide

Toxingenicity Tests

In Vitro Elek test

In Vivo Animal inoculation
rabbit skin test-necrosis

guinea pig challenge test- lethal

low [Fe 2+] induces toxin

Elek test

Animal inoculation

Inject 2 mice with 5ml C.diphtheria cells

one mouse protected with 1000 units C.diphtheriae antitoxin

Autopsy - adrenals hemorrhagic

Control

• Immunization diphtheria toxoid

• Schick test
  • check for antibodies

• Passive immunity
  • Antibodies

• Antibiotics
  • Penicillin & erythromcyin

Schick Test for Diptheria

Epidemics

• Immune individuals
  • may be carriers
  • antibiotics

• Non immune individuals
  • Exposed
    • passive immunity antibodies
  • Not exposed
    • immunize with toxoid

Diphtheria: Russian Federation

Diphtheria in the Soviet Union and NIS

Emerging infectious diseases: 4(4) 1998 Vitek & Wharton

Diphtheria Incidence

Diphtheria in the Russian Federation

The End

Performance Objectives

Key terms, concepts

short answers

Key Terms

• pseudomembrane

Key Terms

• Schick test

• Elek Test

• Diphtheria toxin

• larnygeal diphtheria

• pharyneal diphtheria

Key Organisms

• Corynebacterium

• Listeria

• Erysipelothrix

Key Concepts

Epidemiology of Diphtheria

• Disease/bacterial factors

• Transmission

• Who is at risk

• Geography/ season

• Incidence

• Modes of control

Short Answers

• Construct a table of the virulence factors associated with diphtheria and the biological activity of each

• Use a series of no more than four diagrams to describe the mechanism of action of diphtheria toxin

• Describe the clinical manifestations of diphtheria

• Construct a table listing the common Corynebacteria and the associated diseases.